Method for preparing polyethylene with high melt strength

ABSTRACT

The present invention is an ethylene-based polymer comprising reacting a polyethylene resin with an alkoxy amine derivative corresponding to the formula: 
       (R 1 )(R 2 )N—O—R 3  
 
     where R 1  and R 2  are each independently of one another, hydrogen, C 4 -C 42  alkyl or C 4 -C 42  aryl or substituted hydrocarbon groups comprising O and/or N, and where R 1  and R 2  may form a ring structure together; and where R 3  is hydrogen, a hydrocarbon or a substituted hydrocarbon group comprising O and/or N. Preferred groups for R 3  include —C 1 -C 19 alkyl; —C 6 -C 10 aryl; —C 2 -C 19 akenyl; —O—C 1 -C 19 alkyl; —O—C 6 -C 10 aryl; —NH—C 1 -C 19 alkyl; —NH—C 6 -C 10 aryl; —N—(C 1 -C 19 alkyl) 2 . R 3  most preferably contains an acyl group. The resulting resin has increased melt strength with higher ratio of elongational viscosities at 0.1 to 100 rad/s when compared to substantially similar polyethylene resins which have not been reacted with an alkoxy amine derivative.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. patent application Ser. No.12/685,148, filed Jan. 11, 2010, the disclosure of which is incorporatedherein by reference for purposes of U.S. practice.

BACKGROUND AND SUMMARY OF THE INVENTION

Polyethylene has desirable properties that have helped to make it thehighest volume polymer manufactured. Polyethylene can be made indifferent processes in order to give different properties. Knownfamilies of polyethylene include high density polyethylene (HDPE),linear low density polyethylene (LLDPE), and low density polyethylenemade using high pressure reactors (LDPE). Within these broad classesmany variations exist resulting from different types of polyolefinprocess technologies (for example, solution, slurry or gas phase) orfrom the use of different catalysts (for example, Ziegler-Natta orconstrained geometry catalysts). The desired application requires acareful balance of rheological properties which will lead a person ofskill in the art to select one type of polyethylene over another. Inmany applications, such as blow-molding and blown film applications,melt strength of the polyethylene is a key parameter, frequentlymeasured as elongational viscosity of the polymer.

The melt strength is a practical measurement that can predict materialperformance when submitted at elongational deformations. In meltprocessing good elongational viscosity is important to maintainstability during processes such as coating, blow film production, fiberspinning and foamed parts. The melt strength is related with a number ofmolecular entanglements on molten polymers and relaxation times of eachmolecular structure, which is basically dependant on overall molecularweight and number of branches over critical molecular weight.

Melt strength directly effects several processing parameters such asbubble stability and therefore thickness variation during blow filmproduction; parison formation during blow molding process; saggingduring profile extrusion; cells formation during foaming process; morestable thickness distribution during sheet/film thermoforming.

This property can be enhanced by using resins with higher molecularweight, but such resins will generally require more robust equipment andmore energy use because they tend to generate higher extrusion pressureduring the extrusion process. Therefore, properties must be balanced toprovide an acceptable combination of physical properties andprocessability.

In thick film applications blends of LDPE and LLDPE are used in order toobtain a balance of processability (extruder amps and pressure) and filmmechanical properties. In this blend the LDPE component is theprocessability component whereas the LLDPE is the mechanical endcomponent. Therefore, the ability to decrease the LDPE portion of theblend should increase the mechanical properties of the blend. Throughthis invention, the ability to increase the melt strength of the LLDPEcomponent allows the use of a higher percentage of LLDPE blend, thusincreasing the mechanical properties without sacrificing processabilityor the creation of unacceptable levels of insoluble material.

The present invention is a new process for increasing the melt strengthof polyethylene involving reacting molten polyethylene with analkoxyamine derivative through regular extrusion processing.Accordingly, one aspect of the invention is a method for increasing themelt strength of a polyethylene resin comprising first selecting apolyethylene resin having a density, as determined according to ASTMD792, in the range of from 0.865 g/cm³ to 0.962 g/cm³, and a melt index,as determined according to ASTM D1238 (2.16 kg, 190° C.), in the rangeof from 0.01 g/10 min to 100 g/10 min and then reacting an alkoxy aminederivative with the polyethylene resin in an amount and under conditionssufficient to increase the melt strength of the polyethylene resin.

The present invention is a new process for increasing the elongationalviscosity of polyethylene involving reacting molten polyethylene with analkoxyamine derivative through regular extrusion processing.Accordingly, one aspect of the invention is a method for increasing themelt strength of a polyethylene resin comprising first selecting apolyethylene resin having a density, as determined according to ASTMD792, in the range of from 0.865 g/cm³ to 0.962 g/cm³, and a melt index,as determined according to ASTM D1238 (2.16 kg, 190° C.), in the rangeof from 0.01 g/10 min to 100 g/10 min and then reacting an alkoxy aminederivative with the polyethylene resin in an amount and under conditionssufficient to increase the elongational viscosity of the polyethyleneresin.

The present invention is a new process that increases the elongationalviscosity at low (0.1 s⁻¹) shear rates while maintaining the viscosityat higher shear rates (>100 s⁻¹) such that the ease of processing of thematerial is maintained at typical extrusion conditions. One aspect ofthe invention is that the extruder pressure does not increase more than10% of the comparative resin upon processing the inventive resin at thesame operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of melt strength versus stretching velocity withincreasing additive concentration.

FIG. 2 is a plot of viscosity versus shear rate with increasing additiveconcentration.

FIG. 3 is a plot of melt strength at the plateau region versus meltindex (I₂, g/10 min).

FIG. 4 is a plot of phase angle (°) versus the complex modulus (G*)measured using a constant temperature of 190° C. at a frequency sweep ina TA Instruments “Advanced Rheometric Expansion System (ARES)”

FIG. 5 is a plot of phase angle (°) versus the complex modulus (G*)measured using a constant temperature of 190° C. at a frequency sweep ina TA Instruments “Advanced Rheometric Expansion System (ARES)”

DETAILED DESCRIPTION OF THE INVENTION

In its broadest sense, the present invention is a method for increasingthe melt strength of a polyethylene resin. Polyethylene resin includesall polymers or polymer blends which are derived at least 50% by weightfrom ethylene monomer units. This includes materials known in the art ashigh density polyethylene (HDPE), linear low density polyethylene(LLDPE), and low density polyethylene made using high pressure reactors(LDPE).

The target polyethylene resin selected should have a density, asdetermined according to ASTM D792, in the range of from 0.865 g/cm³ to0.970 g/cm³, more preferably from 0.905 g/cm³ to 0.957 g/cm³ and a meltindex, as determined according to ASTM D1238 (2.16 kg, 190° C.), in therange of from 0.01 g/10 min to 100 g/10 min, more preferably 0.1 g/10min to 15 g/10 min. Suitable target polyethylene resins can be producedwith conventional Ziegler Natta or Chromium catalysts but also withmetallocene or single site catalysts. Such resins may have monomodal ormultimodal molecular weight distributions.

Once the target polyethylene resin is selected, it is reacted with analkoxy amine derivative. For purposes of the present invention “alkoxyamine derivatives” includes nitroxide derivatives. The alkoxy aminederivative is added in an amount and under conditions sufficient toincrease the melt strength of the polyethylene resin. The alkoxy aminederivatives correspond to the formula:

(R₁)(R₂)N—O—R₃

where R₁ and R₂ are each independently of one another, hydrogen, C₄-C₄₂alkyl or C₄-C₄₂ aryl or substituted hydrocarbon groups comprising Oand/or N, and where R₁ and R₂ may form a ring structure together; andwhere R₃ is hydrogen, a hydrocarbon or a substituted hydrocarbon groupcomprising O and/or N. Preferred groups for R₃ include —C₁-C₁₉alkyl;—C₆-C₁₀aryl; —C₂-C₁₉akenyl; —O—C₁-C₁₉alkyl; —O—C₆-C₁₀aryl;—NH—C₁-C₁₉alkyl; —NH—C₆-C₁₀aryl; —N—(C₁-C₁₉alkyl)₂. R₃ most preferablycontains an acyl group.

The preferred compound may form nitroxylradical (R₁)(R₂)N—O* oramynilradical (R1)(R2)N* after decomposition or thermolysis.

A particularly preferred species of alkoxy amine derivative is9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyloctadecanoate which has the following chemical structure:

Examples of some preferred species for use in the present inventioninclude the following:

In general hydroxylamine esters are more preferred with one particularlyfavored hydroxylamine ester being9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyloctadecanoate.

The alkoxy amine derivatives are added in an amount sufficient toincrease the melt strength and/or increase the elongational viscosity tothe desired level. Preferably, the melt strength is increased by atleast 10%, 20%, 25%, 35% or even 50% compared to a similar resin whichhas not been reacted with an alkoxy amine derivative. In general thealkoxy amine derivatives are added in an amount of from 1 to 900 ppm ofthe total amount of polyethylene polymer by weight (that is from 1 to900 parts alkoxy amine derivative per million parts of target resin pluscarrier resin, if any), preferably from 15 to 600 ppm, more preferablyfrom 25 to 400 ppm and still more preferably from 30 to 200 ppm.

The addition to the polyethylene polymer can be carried out in allcustomary mixing machines in which the polymer is melted and mixed withthe additives. Suitable machines are known to those skilled in the art.They are predominantly mixers, kneaders and extruders.

The process is preferably carried out in an extruder by introducing theadditive during processing. Particularly preferred processing machinesare single-screw extruders, contra rotating and co rotating twin-screwextruders, planetary-gear extruders, ring extruders or cokneaders. It isalso possible to use processing machines provided with at least one gasremoval compartment to which a vacuum can be applied. Suitable extrudersand kneaders are described, for example, in Handbuch derKunststoftextrusion, Vol. 1 Grundlagen, Editors F. Hensen, W. Knappe, H.Potente, 1989, pp. 3-7, ISBN.3-446-14339-4 (VoL 2 Extrusionsanlagen1986, ISBN 3-446-14329-7). For example, the screw length can be 1-60times the screw diameter, preferably 35-48 times the screw diameters.The rotational speed of the screw is preferably 10-600 rotations perminute (rpm), more preferably 25-300 rpm. It is also possible to firstprepare a concentrated mixture of the additive in a carrier polyethyleneresin, preferably at 1000 to 10000 ppm, and then introduce thisconcentrate, or “masterbatch”, via an extruder into a meltedpolyethylene using a static mixer to blend the two materials, preferablyat 1 to 20 wt % of the concentrate in the melted resin. The concentratecould be processed in an extruder, preferably at temperatures from 180to 220° C. The temperatures in the static mixer could range from 200 to250° C., with a residence time in the mixer ranging from 1 to 10minutes.

The maximum throughput is dependent on the screw diameter, therotational speed and the driving force. The process of the presentinvention can also be carried out at a level lower than maximumthroughput by varying the parameters mentioned or employing weighingmachines delivering dosage amounts.

If a plurality of components is added, these can be premixed or addedindividually.

The polymers need to be subjected to an elevated temperature for asufficient period of time, so that the desired changes occur. Thetemperature is generally above the softening point of the polymers. In apreferred embodiment of the process of the present invention, atemperature range lower than 280° C., particularly from about 160° C. to280° C. is employed. In a particularly preferred process variant, thetemperature range from about 200° C. to 270° C. is employed.

The period of time necessary for reaction can vary as a function of thetemperature, the amount of material to be reacted and the type of, forexample, extruder used. It is usually from about 10 seconds to 30minutes, in particular from 20 seconds to 20 minutes.

The alkoxy amine derivative can advantageously be added to the mixingdevice by use of a masterbatch. As will be appreciated by those ofordinary skill in the art, the carrier resin for the masterbatch shouldbe chosen to be compatible with the resin to be modified. LDPE highpressure low density polyethylene polymers (referred to in the industryas “LDPE”) were unexpectedly found to be the preferred carrier due tothe lower reactivity as evidenced by little variation of the extrusionpressure during masterbatch production. HDPE may be a better carrier asit will react even less because it does not have tertiary carbons andvery low trisubstituted unsaturation units per 1,000,000 carbons.Another advantage of this invention is the discovery that polypropyleneis not a good carrier for this additive, as it tends to degrade attypical processing temperatures. Another discovery is that the carrierresin should be substantially free of any antioxidant additives,preferably having less than 1,000 ppm of antioxidant additives, as theytend to suppress the activity of the additive.

The preferred carrier resin should be compatible with the application athand; it should have similar viscosity with the target polyethyleneresin with which it is going to be blended. It should be preferably anLDPE or HDPE resin with minimal trisubstituted unsaturation units,preferably fewer than 70 per 1,000,000 carbons. The preferred carrierresin should have a molecular weight (Mn) that is less than 50,000 sothat it is easy to process, as demonstrated by the pressure drop throughthe extruder. The carrier resin could incorporate other additives forprocessing aids but it should preferably be substantially free ofantioxidant compounds, preferably containing less than 1,000 ppm of anyantioxidant compound, preferably less than 500 ppm, more preferably lessthan 100 ppm by weight.

The target polyethylene resin could be a copolymer of ethylene with anyalkene monomer containing 3 to 12 carbons. Preferably, the targetpolyethylene resin should have a level of trisubstituted unsaturationunits per 1,000,000 carbons ranging from 200 to 450. It should have amolecular slightly slower than the carrier resin, as indicated by themelt index (g/10 min). Preferably, the melt index of the targetpolyethylene resin should be higher by 0.2-0.5 units (g/10 min) than thefinal desired resin. Preferably, the polyethylene resin should containminimal or no antioxidant additives, and any additives should bewell-dispersed in the resin prior to being blended with the carrierresin.

The amount of the alkoxy amine derivative material in the carrier resinshould be in the range of 0.1 to 30% by weight, preferably from 0.1 to5%, and more preferably in the range of 0.2 to 1%. The amount of themasterbatch is added so that the alkoxy amine derivative is added to thetarget product in the range of 1 to 900 ppm, preferably from 15 to 600ppm, more preferably from 25 to 400 ppm and still more preferably from30 to 200 ppm. It will readily be understood by one of skill in the artthat the amount of alkoxy amine derivative in the final product will bereduced from the added amounts as the compound reacts with the targetand carrier polyethylene.

Preferably, the amount of the alkoxy amine derivative ingredient shouldbe kept below 1000 ppm to minimize reaction in the carrier resin, reducethe potential for gels in the final product, and be substantiallyreacted out in the final product so that the final product remainsstable with further processing. It should be understood that after thealkoxy amine derivative has been allowed to react with the target resin,it may be desirable to add one or more antioxidant additives, to protectthe properties of the modified target resin. One way to accomplish thisis to blend the resin after reaction with the alkoxy amine derivativewith another resin that is rich in antioxidants.

Testing Methods Melt Strength

Melt strength measurements were conducted on a Gottfert Rheotens 71.97(Göettfert Inc.; Rock Hill, S.C.), attached to a Gottfert Rheotester2000 capillary rheometer. The melted sample (about 25 to 30 grams) wasfed with a Göettfert Rheotester 2000 capillary rheometer, equipped witha flat entrance angle (180 degrees) of length of 30 mm, diameter of 2.0mm, and an aspect ratio (length/diameter) of 15. After equilibrating thesamples at 190° C. for 10 minutes, the piston was run at a constantpiston speed of 0.265 mm/second. The standard test temperature was 190°C. The sample was drawn uniaxially to a set of accelerating nips located100 mm below the die, with an acceleration of 2.4 mm/s². The tensileforce was recorded as a function of the take-up speed of the nip rolls.Melt strength was reported as the plateau force (cN) before the strandbroke. The following conditions were used in the melt strengthmeasurements: plunger speed=0.265 mm/second; wheel acceleration=2.4mm/s²; capillary diameter=2.0 mm; capillary length=30 mm; and barreldiameter=12 mm.

Melt Index

The melt index is used as an indication of molecular weight. Melt indexwas determined using ASTM method D-1238 at 190° C. using a Tinius-OlsenExtrusion Plastometer Model MP987, with orifices with capillarydimensions of 0.0825″ diameter and 0.315″ length; a piston of stainlesssteel with three scribe marks (4.17″, 4.33″, and 5.25″) above the footof the piston; weights of such size that the combined masses of a weightand piston equal 2.16 and 10.00 kg; and a plug gauge for measuring theorifice capillary. The melt index identified as 12 refers to themeasurement with 2.16 kg weight and the melt index identified as I10refers to the measurement using a 10 kg weight.

Density

Samples for density measurements were prepared according to ASTM D4703-10.

Dynamic Mechanical Spectroscopy

Resins were compression-molded into “3 mm thick×1 inch” circular plaquesat 350° F. for five minutes, under 1500 psi pressure in air. The samplewas then taken out of the press, and placed on the counter to cool.

A constant temperature frequency sweep was performed using a TAInstruments “Advanced Rheometric Expansion System (ARES),” equipped with25 mm (diameter) parallel plates, under a nitrogen purge. The sample wasplaced on the plate, and allowed to melt for five minutes at 190° C. Theplates were then closed to a gap of 2 mm, the sample trimmed (extrasample that extends beyond the circumference of the “25 mm diameter”plate is removed), and then the test was started. The method had anadditional five minute delay built in, to allow for temperatureequilibrium. The experiments were performed at 190° C. over a frequencyrange of 0.1 to 100 rad/s. The strain amplitude was constant at 10%. Thestress response was analyzed in terms of amplitude and phase, from whichthe storage modulus (G′), loss modulus (G″), complex modulus (G*),complex viscosity η*, tan (δ) or tan delta, viscosity at 0.1 rad/s(V0.1), the viscosity at 100 rad/s (V100), and the Viscosity Ratio(V0.1/V100) were calculated.

Gel Permeation Chromatography

The Triple Detector Gel Permeation Chromatography (3D-GPC or TD-GPC)system consists of a Waters (Milford, Mass.) 150° C. high temperaturechromatograph (other suitable high temperatures GPC instruments includePolymer Laboratories (Shropshire, UK) Model 210 and Model 220 equippedwith an on-board differential refractometer (RI). Additional detectorscan include an IR4 infra-red detector from Polymer ChAR (Valencia,Spain), Precision Detectors (Amherst, Mass.) 2-angle laser lightscattering (LS) detector Model 2040, and a Viscotek (Houston, Tex.) 150R4-capillary solution viscometer. A GPC with these latter two independentdetectors and at least one of the former detectors is sometimes referredto as “3D-GPC or TD-GPC” while the term “GPC” alone generally refers toconventional GPC. Depending on the sample, either the 15° angle or the90° angle of the light scattering detector is used for calculationpurposes. Data collection is performed using Viscotek TriSEC software,Version 3, and a 4-channel Viscotek Data Manager DM400. The system isalso equipped with an on-line solvent degassing device from PolymerLaboratories (Shropshire, United Kingdom).

Suitable high temperature GPC columns can be used such as four 30 cmlong Shodex HT803 13 micron columns or four 30 cm Polymer Labs columnsof 20-micron mixed-pore-size packing (MixA LS, Polymer Labs). The samplecarousel compartment is operated at 140° C. and the column compartmentis operated at 150° C. The samples are prepared at a concentration of0.1 grams of polymer in 50 milliliters of solvent. The chromatographicsolvent and the sample preparation solvent contain 200 ppm of butylatedhydroxytoluene (BHT) in trichloro benzene (TCB). Both solvents aresparged with nitrogen. The polyethylene samples are gently stirred at160° C. for four hours. The injection volume is 200 microliters. Theflow rate through the GPC is set at 1 ml/minute.

The GPC column set is calibrated by running 21 narrow molecular weightdistribution polystyrene standards. The molecular weight (MW) of thestandards ranges from 580 to 8,400,000, and the standards are containedin 6 “cocktail” mixtures. Each standard mixture has at least a decade ofseparation between individual molecular weights. The standard mixturesare purchased from Polymer Laboratories. The polystyrene standards areprepared at 0.025 g in 50 mL of solvent for molecular weights equal toor greater than 1,000,000 and 0.05 g in 50 mL of solvent for molecularweights less than 1,000,000. The polystyrene standards were dissolved at80° C. with gentle agitation for 30 minutes. The narrow standardmixtures are run first and in order of decreasing amount of the highestmolecular weight component to minimize degradation.

The polystyrene standard peak molecular weights were converted topolyethylene molecular weights using the following equation (asdescribed in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621(1968)):

Mpolyethylene=A(Mpolystyrene)B  (1)

Here B has a value of 1.0, and the experimentally determined value of Ais 0.38.

A first order polynomial was used to fit the respectivepolyethylene-equivalent calibration points obtained from equation (1) totheir observed elution volumes. The actual polynomial fit was obtainedso as to relate the logarithm of polyethylene equivalent molecularweights to the observed elution volumes (and associated powers) for eachpolystyrene standard.

Number, weight, and z-average molecular weights were calculatedaccording to the following equations:

$\begin{matrix}{\overset{\_}{Mn} = \frac{\sum\limits^{i}{Wf}_{i}}{\sum\limits^{i}\left( \frac{{Wf}_{i}}{M_{i}} \right)}} & (2) \\{\overset{\_}{Mw} = \frac{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}} \right)}{\sum\limits^{i}{Wf}_{i}}} & (3) \\{\overset{\_}{Mz} = \frac{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}^{2}} \right)}{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}} \right)}} & (4)\end{matrix}$

Where, Wfi is the weight fraction of the i-th component and Mi is themolecular weight of the i-th component.

The MWD was expressed as the ratio of the weight average molecularweight (Mw) to the number average molecular weight (Mn).

The A value was determined by adjusting A value in equation (1) untilMw, the weight average molecular weight calculated using equation (3)and the corresponding retention volume polynomial, agreed with theindependently determined value of Mw obtained in accordance with thelinear homopolymer reference with known weight average molecular weightof 115,000 g/mol.

Trisubstituted Unsaturation Group Determination Method (FTIR)

Pellets are pressed first to make a thick film of 0.25 mm and thenpressed again to make a thin film of 0.125 mm. The film is then securedon a scan card and then sanded on both sides before being loaded on aNicolet 6700 FTIR instrument. The area under the peak at 909 cm⁻¹ isintegrated to obtain the value of number of trisubstituted unsaturationunits per 1,000,000 carbons using 64 scans with resolution of 2 cm⁻¹.This technique has been calibrated using a known absorbance andconcentration and corrects for film thickness in order to determine theconcentration of the sample.

Using the above measurements, the ratio of the elongational viscositiesat 0.1 to 100 shear rates (s⁻¹) provides an indication of branching inthe polymer and an indication of the effect of the additive. In thisinvention, resins with the additive showed a 10 to 60% increase in theviscosity ratio, preferably an increase of 20 to 40% when compared withthe same resin with no additive.

Resins modified with the additive show a decrease in I₂ of 5% to 25% anda decrease in I₁₀ of 4 to 20%. Therefore, the ratio of I₁₀ to I₂ for theresins increases with increasing amount of additive, indicating extentof change in the polymer.

Resins modified according to the methods of the present invention willexhibit an increase in melt strength of at least 10%, preferably in therange of from 20 to 50% as compared to the same resin which has not beenreacted with the alkoxy amine derivative. Similar performanceimprovement will also be seen with respect to elongational viscosity.For the inventive resins, improvement in melt strength and viscosityperformance is better than anticipated with the changes observed in themelt index measurements.

With the increase in melt strength and/or elongational viscosity, resinsmade according to the present invention are particularly well suited forfabricated articles such as films, sheets, pipes or blow moldedarticles.

Films made using the additive and processing conditions in thisinvention retain the mechanical properties of the polyethylene resinsthat were the base resins without the addition of the alkoxy aminederivative.

EXAMPLES

The four examples (two resins with two different amounts of additiveeach) described below have a similar molecular weight, with differentconcentrations of an alkoxy amine derivative additive. The specificadditive used is9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyloctadecanoate, which is added as an LDPE masterbatch having less than 1%of the additive (Note that the ppm levels reported below refer to theamount of alkoxy amine derivative added and not the amount of the entiremasterbatch added).

The masterbatch is prepared as follows: The alkoxy amine derivativeadditive is compounded with a homopolymer ethylene resin made in ahigh-pressure tubular reactor (that is, an LDPE resin) having a meltindex of 0.7 g/10 min (at 190° C., 2.16 kg ASTM D-1238) and a density of0.925 g/cm³ (ASTM D792). This LDPE resin is the same as Resin Ddescribed below and the additive concentration in the LDPE resin is at5,600 parts per million weight to create a masterbatch.

The LDPE and derivative are compounded in a 30 mm co-rotating,intermeshing Coperion Werner-Pfleiderer ZSK-30 (ZSK-30) twin screwextruder to form a masterbatch. The ZSK-30 has ten barrel sections withan overall length of 960 mm and a 32 length to diameter ratio (L/D). Atwo hole strand die is used without a breaker plate or screen pack. Theextruder consist of a DC motor, connected to a gear box by V-belts. The15 HP motor is powered by a GE adjustable speed drive located in acontrol cabinet. The control range of the screw shaft speed is 1:10. Themaximum screw shaft speed is 500 RPM. A pressure transducer ispositioned in front of the die to measure die pressure.

The extruder has 8 heated/cooled barrel sections along with a 30 mmspacer, which makes up five temperature controlled zones. It has acooled only feed section and a heated only die section, which is heldtogether by tie-rods and supported on the machine frame. Each sectioncan be heated electrically with angular half-shell heaters and cooled bya special system of cooling channels.

The screws consist of continuous shafts on which screw-flightedcomponents and special kneading elements are installed in any requiredorder. The elements are held together radially by keys and keyways andaxially by a screwed-in screw tip. The screw shafts are connected to thegear-shafts by couplings and can easily be pulled out of the screwbarrel for dismantling.

A Conair pelletizer is used to pelletize the blends. It is a 220 voltvariable speed, solid cutter unit. The variable speed motor drives asolid machined cutting wheel, which in turn drives a fixed metal roller.A movable rubber roller presses against the fixed roller and helps pullthe strands by friction into the cutting wheel. The tension on themovable roller may be adjusted as necessary.

The temperatures are set in the feed zone, 4 zones in the extruder, andthe die as:

-   -   Feed: 80° C.    -   Zone 1: 160° C.    -   Zone 2: 180° C.    -   Zone 3: 185° C.    -   Zone 4: 190° C.    -   Die: 210° C.        The screw shaft speed is set at 276 revolutions per minute        (RPM), resulting in an output rate of approximately 52 lb/hr.

The masterbatch defined above is dry-blended with additional amounts ofthe LDPE resin D in order to bring the concentration of the alkoxyaminederivative to a desired level such that when added in an amount of 3% byweight compared to the target polyethylene, the additive will be addedin the amounts shown in the Table. The masterbatch or the dry-blendedmaterial thereof is blended with LLDPE resins B or C using the followingsetup: the masterbatch or the dry-blended material is fed through ahopper into a Sterling 2½ inch single screw extruder which is used asthe side arm conveyer with a rupture disc of 3200 psig. The four heatingzones in the single screw extruder are set at 220° C.

The LLDPE resins B or C are fed through another hopper into aCentury-ZSK-40 extruder (37.13 length-to-diameter ratio extruder, aco-rotating, intermeshing, 40 mm twin screw extruder with 150 Hp drive,244 Armature amps (maximum), and 1200 screw rpm (maximum)). The nineheating zones in the extruder are set as follows: the first at 25° C.,the second at 100° C., and the rest at 200° C.

The polymer melt pump is a Maag 100 cc/revolution pump that helps conveythe molten polymer from the extruder, and through the downstreamequipment. It is powered by a 15 hp motor with a 20.55/1 reduction gear.The pump is equipped with a pressure transmitter and a 5200 psi rupturedisc on the inlet and outlet transition piece. There are heater zones onthe melt pump and the inlet and outlet transition pieces which are setat 220° C.

The melt pump is attached to the extruder and the single screwextruder's flow enters the polymer stream through an injector from thesingle screw side arm extruder. The injector is a ¾ of an inch tubingprotruding into the centerline of a pipe with 3.1 inch internaldiameter.

The polymer coming from the extruder is blended with the single screwextruder resin as it flows through a static mixer with 18 Kenics mixingelement mixer of 3.1 inch internal diameter. The mixing elements have1.3 length-to-diameter ratio. There are seven heating zones in thestatic mixer and are all set to 220° C.

The combined flow then flows through a Gala pelletizer system. The Galais equipped with a 12 hole (2.36 mm hole diameter) Gala die with 4 ofthe holes plugged. The cutter has a 4 blade hub and operates atapproximately 800 ppm. The water temperature in the pelletizer is keptat 30° C.

The amount of the masterbatch or dry-blended masterbatch and resin D isapproximately 3 wt % of the total resin amount. The residence time ofthe masterbatch in the side arm extruder is approximately 20 minutes andthe residence time of the polymer in the static mixer is approximately 3minutes.

The melt strength of each of these examples is measured using GöttfertRheotester 2000 at 190° C. The viscosity is measured using a constanttemperature of 190° C. at a frequency sweep in a TA Instruments“Advanced Rheometric Expansion System (ARES)”. The melt indices aremeasured using ASTM method D-1238 at 190° C. using a Tinius-OlsenExtrusion Plastometer Model MP987. The molecular weights are determinedusing the method described under Testing Methods above.

FIG. 1 shows the melt strength curve versus stretching velocity withincreasing additive concentration. The incorporation of the additivechanges the behavior of resins B and C, increasing the force needed tostretch the molten polymer. The melt strength of resin B with 60 ppmadditive is approximately the same as comparative resin E with the sameamount of resin D but no additive, even though resin E has much lowermelt index than resin B. All resins in this figure contain 3 wt % ofresin D.

FIG. 2 shows the elongational viscosity versus the shear rate frequencymeasured using a constant temperature of 190° C. at a frequency sweep ina TA Instruments “Advanced Rheometric Expansion System (ARES)”. Theincorporation of the additive changes the behavior of Resins B and C atlow shear rates as compared to resins A and E. All resins in this figurecontain 3 wt % of resin D.

FIG. 3 shows the melt strength at the plateau versus the melt index(ASTM method D-1238 at 190° C. with 2.16 kg, in g/10 minutes) for fourZiegler-Natta catalyzed polyethylene resins with no additive (resins A,B, C, and E) and inventive resins B and C with different amounts of theadditive and resin E with 60 ppm additive. Inventive resins B, C and Ehave higher melt strength at the plateau when compared with resins thathave similar melt index and no additive. All resins contain 3 wt % ofresin D.

FIG. 4 shows the phase angle (°) versus the complex modulus (G*)measured using a constant temperature of 190° C. at a frequency sweep ina TA Instruments “Advanced Rheometric Expansion System (ARES)”.Inventive resin B with different amounts of the additive is comparedwith comparative resin A, a resin that does not contain long chainbranches. All resins contain 3 wt % of resin D.

FIG. 5 shows the phase angle (°) versus the complex modulus (G*)measured using a constant temperature of 190° C. at a frequency sweep ina TA Instruments “Advanced Rheometric Expansion System (ARES)”.Inventive resin C with different amounts of the additive is comparedwith comparative resin E, a resin that does not contain long chainbranches. All resins contain 3 wt % of resin D.

Resin Description:

Resin A (Dowlex 61528.20) is a Ziegler-Natta catalyzed polyethyleneresin made in a solution process having melt index of 0.5 g/10 min (at190° C., 2.16 kg ASTM D-1238) and a density 0.921 g/cm³ (ASTM D792).

Resin B (Dowlex TG 2085B) is a Ziegler-Natta catalyzed polyethyleneresin made in a solution process having a melt index of 0.95 g/10 min(at 190° C., 2.16 kg ASTM D-1238) and a density 0.919 g/cm³ (ASTM D792).

Resin C (Dowlex NG 5085B) is a Ziegler-Natta catalyzed polyethylene madein a slurry process having a melt index of 1.3 g/10 min (at 190° C.,2.16 kg ASTM D-1238) and a density of 0.918 g/cm³ (ASTM D792).

Resin D (LDPE 208C/206M) is a homopolymer ethylene resin made in ahigh-pressure tubular reactor having a melt index of 0.7 g/10 min (at190° C., 2.16 kg ASTM D-1238) and a density of 0.925 g/cm³ (ASTM D792).

Resin E (Dowlex 2045) is a Ziegler-Natta catalyzed polyethylene resinmade in a solution process having melt index of 1.0 g/10 min (at 190°C., 2.16 kg ASTM D-1238) and a density 0.920 g/cm³ (ASTM D792).

Resins A, B, C, and E in the table below all additionally contain 3 wt %of resin D.

Density Ratio g/cm³ Melt Viscosity at viscosity at (ASTM ConventionalGPC I₂ I₁₀ I₁₀/I₂ Strength 0.1 rad/s 0.1 to 100 Samples D792) Mn Mw MzMw/Mn (g/10 min) (g/10 min) (g/10 min) (cN) (Pa-s) shear rates Resin A0.921 31,322 150,495 582,495 4.80 0.50 3.96 7.92 6.8 16,356 7.6 Resin B0.919 25,380 110,400 321,500 4.35 0.90 7.23 8.03 4.8 9,700 5.8 (noadditive) Resin B + 0.919 26,870 111,330 320,400 4.14 0.77 6.91 8.97 5.612,015 6.9 30 ppm additive Resin B + 0.918 26,100 111,920 331,200 4.290.69 6.4 9.28 6.4 14,480 8.2 60 ppm additive Resin C 0.918 23,830100,000 291,800 4.20 1.25 10.46 8.37 3.5 6,760 4.8 (no additive) ResinC + 0.918 23,780 100,670 301,400 4.23 1.01 9.36 9.27 4.8 9,810 6.6 60ppm additive Resin C + 0.918 25,470 117,120 359,600 4.60 0.92 8.58 9.295.8 12,040 7.7 80 ppm additive Resin D 0.925 13,670 101,325 296,650 7.410.70 NS NA 16 17,650 22.7 Resin E 0.920 26,031 115,576 360,140 4.44 1.007.96 7.96 4.6 8,395 5.5

From the above examples, it is demonstrated that addition of theadditive results in changes to the molecular weight distribution andsignificantly increases melt strength, at levels compared to comparativeresins A and E, without significantly increasing the molecular weight.For example, the molecular weight distribution is broadened as shown bya minimum of 10% increase in I₁₀I₂ over the comparative resin. The meltstrength increases from 16 to 65% over the comparative resin. It canalso be seen that the addition of the additive results in resins havinghigher melt strength than resins with higher molecular weight that weremade using same polymerization technology (Resins A and E). From theabove examples it is demonstrated that the addition of the additiveresults in resins with higher ratio of elongational viscosities at 0.1to 100 s⁻¹ shear rates, and this manifests in lower pressure droprequirements in an extruder when these resins are processed further. Thechange over the comparative resins in the elongational viscosity ratioranges from 19 to 60%, depending on the set of resins and amount ofadditive used.

The following embodiments are expressly considered to be part of thepresent invention although each embodiment may not be separatelyclaimed.

-   1) A method for increasing the melt strength of a target    polyethylene resin comprising the steps of:    -   a) selecting a target polyethylene resin having a density, as        determined according to ASTM D792, in the range of from 0.865        g/cm³ to 0.962 g/cm³, and a melt index, as determined according        to ASTM D1238 (2.16 kg, 190° C.), in the range of from 0.01 g/10        min to 100 g/10 min;    -   b) reacting an alkoxy amine derivative in an amount less than        900 parts derivative per million parts of total polyethylene        resin with the polyethylene resin under conditions sufficient to        increase the melt strength of the polyethylene resin-   2) The method of embodiment 1 wherein the alkoxy amine derivative    corresponds to the formula:

(R₁)(R₂)N—O—R₃

where R₁ and R₂ are each independently of one another, hydrogen, C₄-C₄₂alkyl or C₄-C₄₂ aryl or substituted hydrocarbon groups comprising Oand/or N, and where R₁ and R₂ may form a ring structure together; and R₃is hydrogen, a hydrocarbon or a substituted hydrocarbon group comprisingO and/or N.

-   3) The method of embodiment 1 wherein the alkoxy amine derivative is    a hydroxylamine ester.-   4) The method of embodiment 3 wherein the hydroxylamine ester is    hydroxylamine ester being    9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyl    octadecanoate-   5) The method of embodiment 1 wherein the alkoxy amine derivative is    added to the target polyethylene resin as a masterbatch comprising    the alkoxy amine derivative along with a carrier resin.-   6) The method of embodiment 5 wherein the carrier resin is selected    from the group consisting of HDPE, LLDPE, and LDPE.-   7) The method of embodiment 6 wherein the carrier resin is LDPE and    the LDPE resin has a vinyl concentration in the range of from 0 to    0.5 vinyls per 1,000 carbons.-   8) The method of embodiment 7 wherein the carrier resin has a vinyl    concentration less than 0.1 vinyls per 1,000 carbons.-   9) The method of embodiment 6 wherein the carrier resin is HDPE and    the HDPE resin has a vinyl concentration in the range of from 0 to    0.5 vinyls per 1,000 carbons.-   10) The method of embodiment 9 wherein the carrier resin has a vinyl    concentration less than 0.05 vinyls per 1000 carbons.-   11) The method of embodiment 6 wherein the carrier resin is    substantially free of antioxidant compounds, in the range of 0 to    1,000 ppm.-   12) The method of embodiment 11 wherein the carrier resin is free of    primary antioxidant compounds.-   13) The method of embodiment 1 wherein the alkoxy amine derivative    is reacted with the polyethylene resin in a reactive extrusion    process.-   14) The method of embodiment 1 wherein the target resin comprises    LLDPE resin derived from ethylene monomer and alpha-olefin    comonomers having three to twelve carbons.-   15) The method of embodiment 1 wherein the target polyethylene resin    comprises LLDPE resin with vinyl content in the range of from 0 to    0.5 vinyls per 1,000 carbons.-   16) The method of embodiment 1 wherein the target resin comprises    blends of LDPE and LLDPE resins.-   17) The method of embodiment 1 wherein the target resin comprises    blends of HDPE and LLDPE resins.-   18) The method of embodiment 1 wherein the target resin comprises    blends of HDPE and LDPE resins.-   19) The method of embodiment 1 wherein the target polyethylene resin    is substantially free of primary antioxidants, preferably in the    range of 0 to 1,000 ppm.-   20) The method of embodiment 1 wherein the alkoxy amine derivative    is added in an amount of from 0.003% to less than 0.09% of the total    amount of polyethylene polymer by weight.-   21) The method of embodiment 5 wherein the masterbatch is produced    by melt extruding a mixture of the carrier resin and the derivative    at extruder temperatures below 250° C.-   22) The method of embodiment 1 wherein the melt strength is    increased by at least 25% compared to a substantially similar    polyethylene resin which has not been reacted with an alkoxy amine    derivative.-   23) The method of embodiment 1 further comprising the step of adding    one or more antioxidants to the target resin after the target resin    has been reacted with the derivative.-   24) A method for increasing the elongational viscosity of a target    polyethylene resin at shear rates below 1 rad/s comprising the steps    of:    -   a) selecting a target polyethylene resin having a density, as        determined according to ASTM D792, in the range of from 0.865        g/cm³ to 0.962 g/cm³, and a melt index, as determined according        to ASTM D1238 (2.16 kg, 190° C.), in the range of from 0.01 g/10        min to 100 g/10 min;    -   b) reacting an alkoxy amine derivative with the target        polyethylene resin in an amount and under conditions sufficient        to increase the elongational viscosity of the target        polyethylene resin.-   25) The method of embodiment 23 wherein the elongational viscosity    of the target polyethylene resin is increased by at least 25%    compared to a substantially similar polyethylene resin which has not    been reacted with an alkoxy amine derivative. The method of    embodiment 23 wherein the elongational viscosity ratio of the target    polyethylene resin at 0.1 to 100 rads is increased by at least 25%    compared to a substantially similar polyethylene resin which has not    been reacted with an alkoxy amine derivative. The use of an alkoxy    amine derivative to improve the melt strength and/or elongational    viscosity of a target polyethylene resin wherein the alkoxy amine    derivative is added to the target polyethylene resin in a reactive    extrusion process.-   28) A fabricated article made from a target polyethylene resin made    according to the method of embodiment 1.-   29) A fabricated article according to embodiment 27 wherein the    article is selected from the group consisting of films, sheets,    pipes or blow molded articles.-   30) A fabricated article according to embodiment 28 which is a film    that retains the mechanical properties as the original resin with    increased melt strength and good processability when compared to    films made of resins which have not been reacted with an alkoxy    amine derivative. A fabricated article according to embodiment 27    that has sufficient antioxidants added in the final processing step    to completely stabilize the resin.-   32) An ethylene-based polymer composition formed by reacting    -   a) a target polyethylene resin having characterized by a resin        having a density, as determined according to ASTM D792, in the        range of from 0.865 g/cm³ to 0.962 g/cm³, and a melt index, as        determined according to ASTM D1238 (2.16 kg, 190° C.), in the        range of from 0.01 g/10 min to 100 g/10 min; with    -   b) b) an alkoxy amine derivative in an amount less than 900        parts alkoxy amine derivative per million parts of total        polyethylene resin in the composition, under conditions        sufficient to increase the melt strength of the target        polyethylene resin.-   33) The ethylene-based polymer composition of embodiment 32 wherein    the target polyethylene resin is further characterized by having    more than 10 trisubstituted unsaturation units/1,000,000 C.-   34) The ethylene-based polymer composition of embodiment 32 wherein    the alkoxy amine derivative corresponds to the formula:

(R₁)(R₂)N—O—R₃

-   -   where R₁ and R₂ are each independently of one another, hydrogen,        C₄-C₄₂ alkyl or C₄-C₄₂ aryl or substituted hydrocarbon groups        comprising O and/or N, and where R₁ and R₂ may form a ring        structure together; and R₃ is hydrogen, a hydrocarbon or a        substituted hydrocarbon group comprising O and/or N.

-   35) The ethylene-based polymer composition of embodiment 32 wherein    the alkoxy amine derivative is a hydroxylamine ester.

-   36) The ethylene-based polymer composition of embodiment 35 wherein    the hydroxylamine ester is hydroxylamine ester being    9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyl    octadecanoate.

-   37) The ethylene-based polymer composition of embodiment 32 wherein    the alkoxy amine derivative is added to the polyethylene resin as a    masterbatch comprising the alkoxy amine derivative along with a    carrier resin.

-   38) The ethylene-based polymer composition of embodiment 37 wherein    the carrier resin is selected from the group consisting of HDPE,    LLDPE, and LDPE.

-   39) The ethylene-based polymer composition of embodiment 38 wherein    the carrier resin is LDPE and the carrier LDPE resin has a    trisubstituted unsaturation unit/1,000,000 C in the range of from 0    to 500.

-   40) The ethylene-based polymer composition of embodiment 39 wherein    the trisubstituted unsaturation unit/1,000,000 C concentration is    less than 100.

-   41) The ethylene-based polymer composition of embodiment 38 wherein    the carrier resin is HDPE and the carrier HDPE resin has a    trisubstituted unsaturation unit/1,000,000 C in the range of from 0    to 500.

-   42) The ethylene-based polymer composition of embodiment 41 wherein    the trisubstituted unsaturation unit/1,000,000 C concentration is    less than 50.

-   43) The ethylene-based polymer composition of embodiment 38 wherein    the carrier resin is characterized by being substantially free of    antioxidant compounds, in the range of from 0 to 1,000 parts    antioxidant per million parts carrier resin.

-   44) The ethylene-based polymer composition of embodiment 43 wherein    the carrier resin is free of primary antioxidant compounds.

-   45) The ethylene-based polymer composition of embodiment 32 wherein    the alkoxy amine derivative is reacted with the polyethylene resin    in a reactive extrusion process.

-   46) The ethylene-based polymer composition of embodiment 32 wherein    the target polyethylene resin comprises LLDPE resin with    trisubstituted unsaturation unit/1,000,000 C in the range of from 0    to 500 ppm.

-   47) The ethylene-based polymer composition of embodiment 32 wherein    the target polyethylene resin is substantially free of primary    antioxidants, preferably in the range of from 0 to 1,000 ppm.

-   48) The ethylene-based polymer composition of embodiment 32 wherein    the alkoxy amine derivative is added in an amount of from 0.003% to    less than 0.09% of the total amount of polyethylene polymer by    weight.

-   49) The ethylene-based polymer composition of embodiment 32 wherein    the melt strength of the target polyethylene resin is increased by    at least 15% compared to a substantially similar polyethylene resin    which has not been reacted with an alkoxy amine derivative.

-   50) An ethylene-based polymer of increased elongational viscosity at    shear rates below 1 rad/s comprising:    a polyethylene resin having a density, as determined according to    ASTM D792, in the range of from 0.865 g/cm³ to 0.962 g/cm³, and a    melt index, as determined according to ASTM D1238 (2.16 kg, 190°    C.), in the range of from 0.01 g/10 min to 100 g/10 min; an alkoxy    amine derivative with the polyethylene resin in an amount and under    conditions sufficient to increase the elongational viscosity of the    polyethylene resin at shear rates below 1 rad/s. The polymer of    embodiment 50 wherein the elongational viscosity is increased by at    least 20% compared to a substantially similar polyethylene resin    which has not been reacted with an alkoxy amine derivative.

-   52) The polymer of embodiment 50 wherein the elongational viscosity    ratio at 0.1 to 100 rad/s is increased by at least 20% compared to a    substantially similar polyethylene resin which has not been reacted    with an alkoxy amine derivative.

-   53) The use of an alkoxy amine derivative to improve the melt    strength and/or elongational viscosity of a polyethylene resin    wherein the alkoxy amine derivative is added to the polyethylene    resin in a reactive extrusion process.

-   54) A fabricated article made from a polyethylene resin made    according to embodiment 32.

-   55) A fabricated article according to embodiment 54 wherein the    article is selected from the group consisting of films, sheets,    pipes or blow molded articles.

-   56) A fabricated article according to embodiment 55 which is a film    that retains the mechanical properties as the original resin with    increased melt strength and good processability when compared to    films made of resins which have not been reacted with an alkoxy    amine derivative.

-   57) A film according to 56 which is a blend of LDPE and LLDPE    resins.

-   58) A film according to 57 which is used in monolayer or multilayer    films.

-   59) A film according to 58 which is used in thick film applications.

-   60) A fabricated article according to embodiment 54 that has    sufficient antioxidants added in the final processing step to    completely stabilize the resin.

Although the invention has been described in considerable detail throughthe preceding description and examples, this detail is for the purposeof illustration and is not to be construed as a limitation on the scopeof the invention as it is described in the appended claims. All UnitedStates patents, published patent applications and allowed patentapplications identified above are incorporated herein by reference.

1. A method for increasing the melt strength of a target polyethylene resin comprising the steps of: a) selecting a target polyethylene resin having a density, as determined according to ASTM D792, in the range of from 0.865 g/cm³ to 0.970 g/cm³, and a melt index, as determined according to ASTM D1238 (2.16 kg, 190° C.), in the range of from 0.01 g/10 min to 100 g/10 min; b) reacting an alkoxy amine derivative in an amount less than 900 parts derivative per million parts of total polyethylene resin with the polyethylene resin under conditions sufficient to increase the melt strength of the polyethylene resin
 2. method of claim 1 wherein the alkoxy amine derivative corresponds to the formula: (R₁)(R₂)N—O—R₃ where R₁ and R₂ are each independently of one another, hydrogen, C₄-C₄₂ alkyl or C₄-C₄₂ aryl or substituted hydrocarbon groups comprising O and/or N, and where R₁ and R₂ may form a ring structure together; and R₃ is hydrogen, a hydrocarbon or a substituted hydrocarbon group comprising O and/or N.
 3. The method of claim 1 wherein the alkoxy amine derivative is a hydroxylamine ester.
 4. The method of claim 3 wherein the hydroxylamine ester is hydroxylamine ester being 9-(acetyloxy)-3,8,10-triethyl-7,8,10-trimethyl-1,5-dioxa-9-azaspiro[5.5]undec-3-yl]methyl octadecanoate
 5. The method of claim 1 wherein the alkoxy amine derivative is added to the target polyethylene resin as a masterbatch comprising the alkoxy amine derivative along with a carrier resin.
 6. The method of claim 5 wherein the carrier resin is selected from the group consisting of HDPE, LLDPE, and LDPE.
 7. The method of claim 6 wherein the carrier resin is LDPE and the LDPE resin has a trisubstituted unsaturation unit per-1,000,000 carbon atoms in the range of from 0 to
 500. 8. The method of claim 7 wherein the carrier resin has a trisubstituted unsaturation unit per 1,000,000 carbon atoms of less than
 100. 9. The method of claim 6 wherein the carrier resin is HDPE and the HDPE resin has a trisubstituted unsaturation unit per 1,000,000 carbon atoms in the range of from 0 to
 500. 10. The method of claim 9 wherein the carrier resin has a trisubstituted unsaturation unit per 1,000,000 carbon atoms less than
 50. 11. The method of claim 6 wherein the carrier resin is substantially free of antioxidant compounds, in the range of 0 to 1,000 ppm.
 12. The method of claim 11 wherein the carrier resin is free of primary antioxidant compounds.
 13. The method of claim 1 wherein the alkoxy amine derivative is reacted with the polyethylene resin in a reactive extrusion process.
 14. The method of claim 1 wherein the target resin comprises LLDPE resin derived from ethylene monomer and alpha-olefin comonomers having three to twelve carbons.
 15. The method of claim 1 wherein the target polyethylene resin comprises LLDPE resin with trisubstituted unsaturation unit per 1,000,000 carbon atoms in the range of from 0 to
 500. 16. The method of claim 1 wherein the target resin comprises a two or more resins selected from the group consisting of LDPE, LLDPE, and HDPE resins.
 17. The method of claim 1 wherein the target polyethylene resin is substantially free of primary antioxidants, preferably in the range of 0 to 1,000 ppm.
 18. The method of claim 1 wherein the alkoxy amine derivative is added in an amount of from 0.003% to less than 0.09% of the total amount of polyethylene polymer by weight.
 19. The method of claim 5 wherein the masterbatch is produced by melt extruding a mixture of the carrier resin and the derivative at extruder temperatures below 250° C.
 20. The method of claim 1 further comprising the step of adding one or more antioxidants to the target resin after the target resin has been reacted with the derivative. 